Crude oil from geological formations can contain a variety of contaminants and foulants, including solid impurities, gasses and minerals. Solid contaminants and foulants can include waxes, asphaltenes, and various hydrates, while contaminating minerals can include sulfur, iron, vanadium, zinc and various mineral/inorganic salts, such as Barite (Barium sulfate), Calcite (Calcium carbonate) and Halite (Sodium chloride). When crude oil is pumped from a formation and transported via drilling and production tubulars and transmission pipelines, these contaminants can precipitate out due to changes in pressure and temperature. This can result in the deposition of such contaminants throughout the system of drilling and production tubulars and pipelines. As these various deposits buildup, they can occlude the various tubulars and deposit on inner surfaces of flow lines, valves and pumps, greatly reducing the pumping efficiency and flow of oil through the drilling, production and tubular systems.
Traditionally, the problem of contaminant buildup has been addressed by various methods including drilling or re-boring of the affected tubular to cut the contaminant buildup from the interior of the pipeline; using chemical solvents to dissolve the various contaminants; using dispersing agents, including surfactants, to obstruct adherence to tubular walls; using hot oil, hot water, or steam to melt the deposits; and using chemical inhibitors in attempts to prevent deposition of foulants. However, each method of addressing contaminant buildup does have its limitations and can involve substantive cost and production downtime.
As an example, crude oil contaminants can be unique for each oil deposit and oil well. Consequently, chemical solvents and methods to remediate such contaminants can be unique to each oil well. Each specific type of contaminant can require a distinct formulation and carrier fluid/solvent for effective application. For example, paraffins are soluble in straight chain alkanes such as hexane and heptane, while asphaltenes are high molecular weight aromatic ring structures and are soluble in aromatic solvents such as xylene and toluene. Also, corrosion inhibitors can include amines, ammonia, and morpholine, while scale dissolvers can include hydrochloric acid or ethylenediamine tetraacetic acid (depending on the kind of mineral causing the scale). Determination of the specific contaminant and determination, formulation and transport of an appropriate treatment can be complex and time consuming.
As currently used, active compounds in these solvents are formulated in a carrier fluid/solvent for ease of delivery or injection into the subject product stream with a simple injection pump. While the use of such chemical additives has shown some effectiveness in inhibiting contaminant depositions, the use of such liquid or solvent based inhibitors greatly increases the cost of transport, storage, and safety of various inhibitor compounds. This is at least due in part to the large volume of solvent needed to maintain the inhibitor in a liquid state, the volatility of the solvent and the noxious nature of many of the solvents.
One system for overcoming these issues comprises the use of a solid chemical as a foulant and/or contaminant inhibitor. The use of a solid chemical allows for a great reduction in transport, storage, and safety costs. However, a problem exists wherein the solid chemical cannot be directly injected into the production process, or wherein the solid chemical cannot maintain a liquid form at ambient pipe temperature. Therefore, a need exists for an efficient, safe, and economical system to provide solid chemical foulant and/or contaminant inhibitors into a production process line.